Systems for delivering liquified gas to an engine

ABSTRACT

A liquified gas delivery system for a motorized platform includes a holding tank configured to receive liquified gas. A first conduit extends from a vapor holding portion of the tank to a valve device. A second conduit extends from a liquid holding portion of the tank to the valve device. Fluid coupled to the valve device is a vaporizer which is in communication with an engine. The valve device selectively withdraws either liquified gas or liquified gas vapor from the tank depending on the pressure within the vapor holding portion of the tank. Various configurations of the delivery system can be utilized for pressurizing the tank during operation.

RELATED APPLICATIONS

This application is a Continuation of pending U.S. application Ser. No.10/621,888, which is a Divisional of now issued U.S. Pat. No. 6,619,273,which is a Continuation of now issued U.S. Pat. No. 6,494,191, which isa Divisional of U.S. application Ser. No. 09/572,523, filed on May 17,2000, now abandoned, which is a Continuation-In-Part of now issued U.S.Pat. No. 6,125,637, which claims priority to U.S. ProvisionalApplication 60/069,697 filed on Dec. 16, 1997.

CONTRACTUAL ORIGIN OF THE INVENTION

The United States Government has certain rights in this inventionpursuant to Contract No. DE-AC07-94ID13223, Contract No.DE-AC07-99ID13727, and Contract No. DE-AC07-05ID14517 between the UnitedStates Department of Energy and Battelle Energy Alliance, LLC.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to fuel delivery systems. Morespecifically, the present invention relates to systems and methods fordelivering liquified gas from a holding tank to an engine.

2. Present State of the Art

The increasing output of automobile emissions and the decreasing supplyof oil reserves has motivated the search for alternative motor vehiclefuels. One alternative fuel is natural gas. Natural gas is clean burningand can be stored in a dense, high energy liquid form. Liquefyingnatural gas is accomplished by cooling the natural gas to a cryogenictemperature, typically below −260° F., which condenses the gas into aliquid. Working with and keeping natural gas at a cryogenic temperature,however, creates inherent problems. Furthermore, natural gas, prior tocombustion, is a harmful greenhouse gas. As such, it is important thatthe escape of any natural gas be minimized to prevent increased harm tothe atmosphere.

In one approach to using natural gas in automobiles, the natural gas isinitially stored in large tanks at refueling stations. The large tanksmaintain the fuel at a cryogenic temperature so as to keep the naturalgas in a dense liquid state. Smaller insulated fuel tanks are locatedwithin the automobiles and can be filled with the liquified natural gasat a refueling station. As discussed above, it is desirable to store thenatural gas in a liquified state. It is also beneficial, however, tohave the automobile fuel tank sufficiently pressurized so that the fueltherein will automatically flow to the vehicle engine. Although a pumpcan be used to deliver the fuel to the engine, use of a pump requiresenergy. Furthermore, pumping natural gas at cryogenic temperatures hasbeen found to be problematic.

In one approach to obtaining the desired pressure within the automobilefuel tank, systems have been incorporated into refueling stations whichwarm the liquified natural gas as it is pumped into the automobile fueltank. By heating the liquified natural gas to a desired temperature, aportion of the liquified natural gas vaporizes within the fuel tank toproduce the desired pressure. The pressure created within the fuel tankas a result of warming the fuel is called “saturation pressure.”Although this process achieves the desired objective, it also producesseveral problems.

For example, the systems for heating the natural gas at the refuelingstation are time consuming and expensive to operate and build.Furthermore, as a result of warming the natural gas, less natural gascan be stored within the fuel tank. In addition, since all of thenatural gas that is pumped into the automobile fuel tank is heated, thefuel must be used relatively quickly to prevent having to vent any ofthe natural gas to the atmosphere. Although the automobile fuel tank isinsulated, once the liquified natural gas is pumped therein, the fuelbegins to slowly warm towards an equilibrium with the outsidetemperature. As the fuel warms, the pressure within the tank increases.Once the tank reaches a designed relief pressure, a pressure reliefvalve is opened allowing a portion of the natural gas to escape into theatmosphere, thereby decreasing the internal pressure. The time periodthat a tank can hold natural gas without having to vent is called the“hold time.” As previously discussed, releasing natural gas into theatmosphere is both wasteful and potentially harmful.

In contrast, if the natural gas is consumed too quickly, the pressurewithin the fuel tank can drop below the required operating pressure. Asliquified natural gas is consumed, the volume of the vapor holdingportion of the fuel tank is increased. As this volume increases, aportion of the liquified natural gas is vaporized to fill the spacewithin the fuel tank. Vaporization of natural gas is an endothermicprocess which absorbs heat. Accordingly, as the natural gas within thefuel tank is vaporized, the temperature and thus pressure within thefuel tank decreases. If liquified natural gas is consumed too quickly,the pressure will drop below the operating pressure.

In an alternative approach to pressurizing the automobile fuel tank, aheater is directly coupled with the automobile fuel tank for heating theliquified natural gas therein. The problem with this approach is that ittakes both time and energy to heat the fuel within the fuel tank.Furthermore, the same problem exists of having to use the natural gasrelatively quickly to prevent having to vent portions of the natural gasto the atmosphere.

Other problems in conventional liquified natural gas systems relate tothe lines extending from the fuel tank to the engine. Many of the priorart systems require the use of electronic switches, solenoids, andcomputers to operate them. The use of such electronics is expensive,increases the complexity of the system, decreases the reliability of thesystem, and consumes large amounts of energy.

The same problems as discussed above for vehicles are also applicable tousing natural gas or other liquified gases to run engines that are notvehicle related.

SUMMARY AND OBJECTS OF THE INVENTION

It is an object of the present invention to provide improved deliverysystems and methods for delivering liquified gases to an engine.

Another object of the present invention is to provide improved deliverysystems which do not require a liquified gas to be warmed as it istransferred from a refueling facility to a holding tank for operating anengine.

Yet another object of the present invention is to provide deliverysystems which do not require all of the liquified gas disposed withinthe holding tank to be warmed therein.

Still another object of the present invention is to provide deliverysystems which significantly increase the hold time of the liquified gasin the tank.

A further object of the present invention is to provide delivery systemsfor liquified gas which maintain a desired pressure within the holdingtank substantially independent of the gas consumption rate.

Yet another object of the present invention is to provide deliverysystems which enable relatively quick pressurization of the tank holdingthe liquified gas.

Finally, an additional object of the present invention to providedelivery systems which provide fuel lines extending from the tank to theengine that do not require the use of electronic switches, solenoids orcomputers to function.

To achieve the foregoing objects, and in accordance with the inventionas embodied and broadly described herein, a liquified gas deliverysystem and method are provided for use with an engine mounted on amobile or stationary vehicle. The liquified gas delivery system includesan insulated holding tank configured to receive a liquified gas atsaturated liquid/gas conditions. The holding tank bounds a chamber whichincludes a liquid holding portion for holding liquified gas and a vaporholding portion for holding liquified gas vapor. A vapor conduit extendsfrom the vapor holding portion of the tank to a valve device such as aneconomizer valve or ecoshunt valve. A liquid conduit extends from theliquid holding portion of the tank to the valve device. A transitionconduit extends from the valve device to a vaporizer.

The valve device is configured to operate in one of two positionsdepending on the pressure within the vapor holding portion of the tank.When pressure within the vapor holding portion of the tank is below aselect pressure, the valve device facilitates the flow of the liquifiedgas from the tank to the vaporizer. When the pressure within the vaporholding portion of the tank exceeds the select pressure, the valvedevice blocks the flow of liquified gas and facilitates the flow of theliquified gas vapor from the tank to the vaporizer. Once sufficientliquified gas vapor has been removed from the tank to drop the pressuretherein below the select pressure, the valve device again facilitatesthe flow of the liquified gas from the tank to the vaporizer.

The vaporizer is heated with coolant from the engine. As liquified gasis passed through the vaporizer, the elevated temperature causes theliquified gas to flash into a vapor. A delivery conduit extends from thevaporizer to the engine for delivering the liquified gas vapor thereto.A return conduit having a check valve coupled therewith extends from thedelivery conduit to the vapor holding portion of the tank. Feeding ofthe liquified gas vapor from the return conduit to the vapor holdingportion of the tank functions to pressure the tank.

It is desirable to keep the liquified gas within the tank at the lowesteconomical temperature. At such a temperature, however, there may beinsufficient saturation pressure within the vapor holding portion of thetank to drive the liquified gas from the tank to the engine. Until suchtime that the liquified gas warms up from the outside environment to apoint that it produces the required saturation pressure, the liquifiedgas vapor feeding from the return conduit to the vapor holding portionof the tank functions to create the required pressure to operate thesystem.

To enable effective pressurization of the tank using the return conduit,the vaporizer is most effective when positioned a required distancebelow the surface of the liquified gas in the tank. Specifically, thehead between the surface level of the liquified gas and the point in thevaporizer where the liquified gas is vaporized must be sufficientlylarge to create a required pressure on the vaporized gas leaving thevaporizer. This required pressure must be greater than the summation ofthe pressure losses on the gas as it passes from the tank through thevalve device, vaporizer, and back to the tank. As a practical matter, toenable operation of the engine at low levels of fuel within the tank,the vaporizer is preferably positioned below the elevation of the tank.

The systems of the invention have several advantages over priorconventional systems. For example, in the present inventive system theliquified gas within the holding tank can be maintained at its lowestpossible temperature. As a result, it is not necessary to incorporatesystems for warming the liquified gas as it is transferred from arefueling facility, or systems for warming the liquified gas within thetank. Furthermore, since the liquified gas is maintained at a lowtemperature, the hold time for the tank is much longer than conventionalsystems. In addition, the present system can continually regulate thepressure within the tank independent of the consumption rate. Finally,the system can be operated in a passive configuration which does notrequire the use of electronic solenoids, switches, or computers to run.

These and other objects, features, and advantages of the presentinvention will become more fully apparent from the following descriptionand appended claims, or may be learned by the practice of the inventionas set forth hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to illustrate the manner in which the above-recited and otheradvantages and objects of the invention are obtained, a more particulardescription of the invention briefly described above will be rendered byreference to specific embodiments thereof which are illustrated in theappended drawings. Understanding that these drawings depict only typicalembodiments of the invention and are not therefore to be consideredlimiting of its scope, the invention will be described and explainedwith additional specificity and detail through the use of theaccompanying drawings in which:

FIG. 1 is a perspective view of a vehicle incorporating the liquifiedgas delivery system of the present invention;

FIG. 2 is a schematic representation of one embodiment of the liquifiedgas delivery system incorporated into the vehicle in FIG. 1;

FIG. 3 is a schematic cross-sectional view of a valve device used in theliquified gas delivery system shown in FIG. 2;

FIG. 4 is a schematic representation of an alternative embodiment of theliquified gas delivery system shown in FIG. 2;

FIG. 5 is a schematic cross-sectional view of a valve device used in theliquified gas delivery system shown in FIG. 4;

FIGS. 6-12 are schematic representations of alternative embodiments ofthe liquified gas delivery system shown in FIG. 2;

FIG. 13 is a schematic cross-sectional view of a valve device accordingto an alternative embodiment of the invention;

FIG. 14 is a schematic cross-sectional view of a valve device accordingto another alternative embodiment of the invention; and

FIG. 15 is a schematic cross-sectional view of a valve device accordingto a further alternative embodiment of the invention;

FIGS. 16A and 16B are schematic representations of alternativeembodiments for connecting a valve device to a holding tank according tothe invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to systems and methods for deliveringsaturated liquified gases from a holding tank to an engine mounted on avehicle. As used in the specification and appended claims, the term“vehicle” is defined as any motorized platform, whether stationary ormobile. By way of example and not by limitation, mobile vehicles caninclude cars, pickup trucks, cargo trucks, buses, trains, trailers,tractors, construction vehicles, off-road equipment, farming vehicles,aircraft, helicopters, and the like; stationary vehicles can includemotorized process equipment such as compressors, generators, heating andair conditioning systems, and the like. Virtually any motorized platformcan use the system of the invention where the prime mover is an internalor external combustion device for generating energy.

Referring to the drawings, wherein like structures are provided withlike numerical reference designations, FIG. 1 depicts one embodiment ofa vehicle 10 in the form of a bus which incorporates features of thepresent invention. Vehicle 10 is shown having a chassis 12 with aholding tank 14 mounted thereon. The term “chassis” as used in thespecification and appended claims is intended to broadly include theframe and/or body of the vehicle.

Holding tank 14 is insulated, preferably by having a vacuum barrier, andis configured to receive and retain liquified gas at saturatedconditions. The expression “saturated conditions” as used herein refersto the given temperature and pressure at which a gas/liquid phaseequilibrium exits for a particular substance. The tank 14 is filled withliquified gas through an inlet 16. The expression “liquified gas” asused in the specification and appended claims is broadly intended toinclude gases that exist in a gaseous state at ambient conditions andrequire saturated conditions to exist in a liquid state. The liquifiedgas can include various substances that are fuels or oxidizers. By wayof example and not limitation, liquified gas fuels can include hydrogen,hydrocarbon gases such as methane, ethane, propane, butane, natural gas,and the like, as well as various mixtures thereof; liquified gasoxidizers can include oxygen, fluorine, chlorine, mixtures thereof, andthe like.

Preferably, tank 14 is adapted to receive and retain liquified gas at orbelow a given saturated condition temperature. For example, methane gasbecomes liquified at a temperature of about −220° F. under a pressure ofabout 65 psi. It will be appreciated by those skilled in the art thatthe saturated condition temperature can vary widely depending on thespecific gas utilized and the operating pressures under which the gas isemployed.

Depicted in FIG. 2 is a schematic representation of one embodiment of aliquified gas delivery system 18 that can be incorporated into vehicle10. As depicted in FIG. 2, tank 14 comprises a liquid holding portion 20for holding liquified gas 22 and a vapor holding portion 24 for holdingvaporized gas 26. Liquid holding portion 20 and vapor holding portion 24are separated by the surface of liquified gas 22 defined by dotted line28. The volume of liquid holding portion 20 and vapor holding portion 24vary inversely depending on the volume of liquified gas 22 within tank14. That is, as liquified gas 22 is consumed, surface 28 of liquifiedgas 22 lowers, thereby decreasing the volume of liquid holding portion20 and increasing the volume of vapor holding portion 24.

Tank 14 is filled with liquified gas 22 by passing liquified gas 22through inlet 16 and into a filling conduit 42. Filling conduit 42 isfluid coupled with a vapor conduit 32 having a first end 34 disposedwithin vapor holding portion 24 and an opposed second end 36 fluidcoupled to an economizer valve 38. Mounted at first end 34 of vaporconduit 32 are one or a plurality of spray nozzles 40. As a result ofrelative pressures, liquified gas 22 entering vapor conduit 32 fromfilling conduit 42 travels to first end 34 where it is sprayed into tank14 through nozzles 40.

Nozzles 40 serve a unique purpose. Under normal operating conditions,once vehicle 10 has run for a sufficient period of time to substantiallyempty tank 14 of liquified gas 22, the remaining vaporized gas 26 withintank 14 is at a relatively high saturation pressure. This is because theremaining gas within tank 14 has been warmed by the outside environmentduring operation. During refueling, as the cold liquified gas is sprayedinto tank 14 over the liquified gas vapor therein, the liquified gasvapor is cooled and condensed, thereby reducing the saturation pressure.As a result, tank 14 can be filled quickly and to a much greater extentwithout having to vent liquified gas vapor into the atmosphere. Thereare of course a variety of single or multiple spray nozzles that can beused. Furthermore, various dripping or other mechanisms can be used tohelp disperse the liquified gas over the vaporized gas within tank 14.

In one embodiment of the present invention, means are provided fordelivering liquified gas from tank 14 to an engine 30. Engine 30 islikewise mounted to chassis 12 of vehicle 10. In more specificembodiments, means are provided for passively delivering the gas fromtank 14 to engine 30 while automatically and passively maintaining apressure within a predetermined range within vapor holding portion 24 oftank 14. As used in the specification and appended claims, the term“passively” defines a system that is self-regulating without the use ofelectronically actuated flow controlling devices such as solenoids orother valves or switches.

By way of example of the above delivery means and not by limitation,vapor conduit 32 extends from vapor holding portion 24 of tank 14 toeconomizer valve 38, as discussed above. Similarly, a liquid conduit 44has a first end 46 positioned within liquid holding portion 20 of tank14 and an opposing second end 48 fluid coupled to economizer valve 38.An opening at first end 46 of liquid conduit 44 enables liquified gas 22to travel through liquid conduit 44 to economizer valve 38.

The present invention also includes control means for automaticallywithdrawing a select gas chosen from either liquified gas 22 orvaporized gas 26 from tank 14 based on the pressure within tank 14. Byway of example and not by limitation, depicted in FIG. 3 is oneembodiment of a valve device in the form of an economizer valve 38.Economizer valve 38 includes a housing 50 having an interior surface 51bounding an elongated chamber 52. Chamber 52 extends from a bottom end54 to a top end 56. Longitudinally disposed within chamber 52 is a rod60. Rod 60 also has a bottom end 62 and an opposing top end 64.Extending between top end 64 of rod 60 and housing 50 is a resilientlycompressible spring 66. Radially projecting out at bottom end 62 of rod60 is an annular seal 68. Radially inwardly projecting from interiorsurface 51 around bottom end 62 of rod 60 is a circular flange 96 havingan opening 97 extending therethrough. Flange 96 is configured such thatwhen seal 68 is biased thereagainst, opening 97 is sealed closed.

Extending across chamber 52 and sealed against rod 60 and interiorsurface 51 are three distinct flexible diaphragms which divide chamber52 into four isolated compartments. Specifically, a flexible firstdiaphragm 74 bounds a first compartment 76 extending between firstdiaphragm 74 and top end 56 of chamber 52. First compartment 76 housesspring 66 and communicates to the exterior through an opening 58. Anisolated second compartment 78 is positioned between first diaphragm 74and a flexible second diaphragm 80. A third compartment 82 is formedbetween second diaphragm 80 and a flexible third diaphragm 84. Finally,a fourth compartment 86 is bounded between third diaphragm 84 and bottomend 54 of chamber 52.

Vapor conduit 32 extends through housing 50 and communicates with secondcompartment 78. A bypass conduit 88 extends from vapor conduit 32 tothird compartment 82. A check valve 90 is positioned within bypassconduit 88. A transition conduit 92 extends through housing 50 fromthird compartment 82 to the exterior of economizer valve 38. Liquidconduit 44 extends through housing 50 and communicates with fourthcompartment 86. A bypass conduit 94 extends from fourth compartment 86,at a side of flange 96 opposite liquid conduit 44, to transition conduit92.

Economizer valve 38 is configured to automatically operate in one of twopositions for withdrawing either vaporized gas 26 from tank 14 orliquified gas 22 from tank 14. The determination of which of the two gasforms is removed from tank 14 depends on the pressure within vaporholding portion 24. That is, economizer valve 38 moves between one ofthe two positions when a select pressure is reached within vapor holdingportion 24. The select pressure is manually set and can vary dependingon the intended use and system parameters. The select pressure istypically in a range between about 20 psi to about 140 psi, with about60 psi to about 100 psi being preferred, and about 60 psi to about 80psi being more preferred.

By way of example, when the pressure within vapor holding portion 24 isbelow the select pressure, liquified gas 22 flows through supply conduit44 into fourth compartment 86, through opening 97 in flange 96, andthrough bypass conduit 94 where it eventually exits through transitionconduit 92. Check valve 90 prevents liquified gas 22 from passing intovapor conduit 32. As the pressure increases within vapor holding portion24, for reasons as will be discussed later, the pressure correspondinglyincreases within second compartment 78. This is because secondcompartment 78 and vapor holding portion 24 are coupled together byvapor conduit 32.

Since first compartment 76 is under atmospheric conditions as a resultof opening 58, as second compartment 78 is pressurized, first diaphragm74 is pressed into first compartment 76 causing rod 60 to compressagainst spring 66. The resistance of spring 66 is manually set such thatas the pressure within second compartment 78 reaches the selectpressure, rod 60 is sufficiently compressed against spring 66 so thatseal 68 is biased against flange 96, thereby sealing opening 97 closed.Vaporized gas 26 is then permitted to pass from vapor conduit 32 throughbypass conduit 88 into third compartment 82 and subsequently outtransition conduit 92. Once the pressure within second compartment 78drops below the select pressure, spring 66 pushes rod 60 downward so asto separate seal 68 and flange 96, thereby again allowing liquified gas22 to pass therethrough. Standard economizer valves, such as thatdiscussed above, can be purchased from MVE out of Bloomington, Minn.

Returning to FIG. 2, the select gas leaving economizer valve 38 travelsthrough transition conduit 92 to a vaporizer 100. Vaporizers, alsoreferred to as heat exchangers, can be purchased off the shelf. Aconventional vaporizer comprises a coil 102 having an inlet end 104 andan outlet end 106. At least a portion of coil 102 is enclosed within ahousing 108. In the present invention, housing 108 is fluid coupled to apair of heating conduits 110 and 112 which continually cycle heatedradiator fluid between housing 108 and engine 30. As liquified gas 22passes through coil 102 within housing 108, the heat from the radiatorfluid causes the liquified gas to flash to a vapor.

The present invention also provides means for delivering at least aportion of the select gas from vaporizer 100 to engine 30. By way ofexample and not by limitation, a delivery conduit 114 extends fromvaporizer 100 to engine 30. To help optimize the process, a flowregulator 115 can be attached to delivery conduit 114. Means are alsoprovided to enable delivery of a portion of the select gas fromvaporizer 100 back to tank 14, for maintaining an operating pressurewithin the vapor holding portion of tank 14. By way of example and notby limitation, a return conduit 116 having a check valve 118 formedthereon extends from delivery conduit 114 to filling conduit 42. As aresult, depending on the rate of fuel consumption by engine 30, aportion of the liquified gas vapor from delivery conduit 114 can travelthrough return conduit 116, filling conduit 42 and vapor conduit 32where it subsequently enters into vapor holding portion 24 of tank 14.The feeding or at least communication of liquified gas vapor fromdelivery conduit 114 to vapor holding portion 24 provides the neededpressure for driving liquified gas 22 through the system to engine 30without the need for a pump. When the pressure within vapor holdingportion 24 exceeds the desired or select pressure, economizer valve 38pulls off the liquified gas vapor as previously discussed.

There are of course, a variety of alternative conduit configurationsthat can be used to feed the liquified gas vapor back to vapor holdingportion 24. By way of example, the liquified gas vapor can be fed backinto the economizer valve, as will be illustrated in a subsequentembodiment. Furthermore, a conduit could be formed that extends directlybetween delivery conduit 114 and vapor holding portion 24. Furthermore,a conduit can be formed to extend directly between vaporizer 100 andvapor holding portion 24. Other embodiments will be set forth later inthe disclosure.

One of the novel concepts of the present invention is the positioning ofvaporizer 100 relative to tank 14. To enable the vaporized gas leavingvaporizer 100 to most efficiently flow back into vapor holding portion24, a maximum elevation difference or head H should be achieved betweensurface 28 of liquified gas 22 and the point in vaporizer 100 where theliquified gas is vaporized. Specifically, head H must be sufficientlylarge to produce a pressure on the vaporized gas leaving vaporizer 100that is greater than the summation of all the pressure losses as aresult of the gas passing from tank 14 through economizer valve 38,vaporizer 100, and the various conduits back to vapor holding portion24. If head H is insufficient to overcome these pressure losses, theliquified gas vapor will not flow back into vapor holding portion 24 andthus pressure will not build therein. Since surface 28 of liquified gas22 continually drops as the gas is consumed in engine 30, to maintainoperation at low fuel levels it is preferred that vaporizer 100 bepositioned below tank 14.

The greater the head H, the faster in which vapor holding portion 24will be pressurized. The rate at which vapor holding portion 24 ispressurize is an important consideration for startup time afterrefueling. That is, once tank 14 is filled with liquified gas, thepressure within vapor holding portion 24 is typically insufficient todeliver liquified gas to engine 30. Alternative heating sources such assolar radiation, batteries, or using gasoline to run engine 30 can beused for heating vaporizer 100 and thus pressurizing vapor holdingportion 24. However, it is desirable to be able to pressurize vaporholding portion 24 as quickly as possible so as to enable operationusing the liquified gas.

By increasing the head H, pressure on the liquified gas vapor isincreased, thereby increasing the rate and shortening the time forpressurizing vapor holding portion 24. In one embodiment, vapor holdingportion 24 of tank 14 can be pressurized to a select operationalpressure in a period of time after refueling less than about 15 minutes,more preferably in less than about 10 minutes, and most preferably inless than about 5 minutes. In some embodiments, it is also desirablethat vaporizer 100 be positioned below tank 14 at a preselecteddistance. An increased distance between the tank and vaporizerpositioned therebelow has been found to improve the performance of theliquified gas delivery system.

Depicted in FIG. 4 is an alternative embodiment of a liquified gasdelivery system 120. Like structural elements between delivery system 18and 120 are identified by like reference characters. In contrast todelivery system 18, filling conduit 42 can directly fluid couple withtank 14 through nozzles 40. Furthermore, vapor conduit 32 need notcommunicate with nozzles 40. Return conduit 116 has been removed andreplaced with a conduit 122. Conduit 122 has a check valve 124 formedtherewith and extends from delivery conduit 114 to economizer valve 38.As depicted in FIG. 5, economizer valve 38 has been altered to haveconduit 122 extending through housing 50 to second compartment 78. Checkvalve 124 prevents liquified gas vapor from passing from secondcompartment 78 through conduit 122. Check valve 124, however, doesenable the liquified gas vapor to pass from delivery conduit 114 intosecond compartment 78 for pressurization of vapor holding portion 24,thereby producing the same effect as previously discussed witheconomizer valve 38 in FIG. 3.

FIG. 6 is an alternative embodiment of a liquified gas delivery system126 in which one way check valve 118 of delivery system 18 has beenreplaced by an electronic solenoid 128. Solenoid 128 electronicallyopens and closes conduit 116.

FIG. 7 is an alternative embodiment of a liquified gas delivery system130. This embodiment can be used when it is impossible or impractical toposition vaporizer 100 at a position sufficiently far below surface 28of liquified gas 22 to obtain the desired head H. In this embodiment, asmaller vaporizer 132 can be positioned at a preferred distance belowtank 14. The vaporizer 132 is an example of a means for maintaining anoperating pressure within the vapor holding portion of the tank. Aconduit 134 having a one way check valve 138 fluid couples transitionconduit 92 to vaporizer 132. Conduit 134 thus provides liquified gas tovaporizer 132. A conduit 136 delivers the gas vaporized by vaporizer 132to vapor conduit 32, thereby pressurizing vapor holding portion 24 insubstantially the same way as previously discussed with regard to FIG.2. Vaporizer 132 can be heated using a variety of alternative designs,for example, coolant can be taken from engine 30. Alternatively, solaror battery operated heating devices can be used.

Depicted in FIG. 8 is a fluid delivery system 140 similar to fluiddelivery system 130 depicted in FIG. 7. In contrast, however, conduit134 of fluid delivery system 140 is fluid coupled to supply conduit 44rather than transition conduit 92. Furthermore, one way check valve 138has been replaced by an electronically operated solenoid valve 142.

Depicted in FIG. 9 is a fluid delivery system 146 also comparable tofluid delivery system 130. In fluid delivery system 146, however,conduit 136 is fluid coupled to economizer valve 38 in substantially thesame way that conduit 122 is coupled to economizer valve 38 aspreviously discussed with regard to FIGS. 4 and 5.

Depicted in FIG. 10 is yet another alternative embodiment of a fluiddelivery system 150. In this embodiment, when vaporizer 100 ispositioned too high relative to level 28 of liquified gas 22 to drivefuel into engine 30, solenoid 152 on transition conduit 92 closescausing the gas to flow from transition conduit 92 to a small reservoir154 through a conduit 156. A one way check valve 158 prevents a backflow of liquified gas vapor. In turn, a conduit 160 feeds liquified gas22 from reservoir 154 to a secondary vaporizer 162 positioned at adesired elevation relative to tank 14. Vaporizer 162 is also coupled tovapor conduit 32 by a conduit 161 for pressurizing vapor holding portion24 as previously discussed with regard to FIG. 2. A conduit 164 allowsliquified gas vapor to travel from reservoir 154 back to vaporizer 100.Once sufficient pressure is built within the system, solenoid 152 can beopened to allow direct flow into vaporizer 100.

Depicted in FIG. 11 is a fluid delivery system 166 similar to fluiddelivery system 150 depicted in FIG. 10. In contrast, however, conduit164 now extends from reservoir 154 to delivery conduit 114. Solenoidvalve 152 has also been moved from transition conduit 92 to conduit 164.When solenoid valve 152 is open, liquified gas passes from transitionconduit 92 into reservoir 154 through conduit 156. When solenoid 152 isclosed, liquified gas within reservoir 154 travels through vaporizer 162and back into conduit 32 for pressurizing the system.

Depicted in FIG. 12 is a fluid delivery system 168 substantially thesame as that depicted in FIG. 10 except that an additional solenoid 166has been positioned on conduit 164. When solenoid 166 is closed,liquified gas in reservoir 154 is vaporized in vaporizer 162 andreturned to vapor conduit 32 for pressurizing the system.

FIG. 13 is a schematic cross-sectional view of a valve device in theform of an ecoshunt valve 200 according to an alternative embodiment ofthe invention. The valve 200 is another example of a control means whichperforms the function of automatically withdrawing a select gas, chosenfrom either a liquified gas or a liquified gas vapor, from the tankbased on the pressure within the tank. The valve 200 can be used inplace of the economizer valve discussed previously such as in deliverysystem 18 of FIG. 2. The valve 200 combines the functions of theeconomizer valve with shunt control and thus is called an “ecoshunt”valve. The valve 200 performs the functions of proportioning fluid flowto an engine between an all gas phase fluid comprising liquified gasvapor and an all liquid phase fluid comprising liquified gas, whiledirecting available excess liquid phase fluid back to the tank formaintaining an operating pressure therein. The valve 200 may beconstructed to retrofit to current tank designs with some modificationto the tank, or can be integrated with a tank design for improvedreliability and robustness.

As depicted in FIG. 13, valve device 200 includes a housing 202 havingan interior surface 204 bounding a pair of first and second interiorchambers 206 and 208, which are separated by a dividing wall 209.Longitudinally disposed between chambers 206 and 208 is a proportioningspool 210. The spool 210 includes an enlarged head portion 212 disposedin chamber 208 which tapers to an elongated stem portion 214 thatextends into chamber 206 through a passageway 216 in dividing wall 209.

A shunt system is provided in spool 210 and includes a shunt port 218 instem portion 214 that communicates with a shunt channel 220 which passesthrough head portion 212. A shunt check valve 222 is provided in channel220. The shunt check valve 222 is one example of a means for regulatingthe flow of liquified gas through channel 220. Other regulating meanswill be readily apparent to those skilled in the art, such as variousother valve configurations. The shunt system is an example of a meansfor maintaining an operating pressure within the vapor holding portionof a tank.

A pressure set screw 224 passes through housing 202 into chamber 206 andis operatively connected to stem portion 214 of spool 210 by way of apressure control spring 226. The pressure set screw 224 and associatedpressure control spring 226 are an example of a means for positioningspool 210 within chambers 206 and 208. It will be understood by thoseskilled in the art that a variety of other configurations may beutilized to accomplish this function, such as an electrical controldevice which is discussed in further detail hereafter. A dust cover 228can be placed over pressure set screw 224 if desired.

A diaphragm 230 extends across chamber 206 and is sealed against stemportion 214 and interior surface 204, thereby dividing chamber 206 intotwo isolated compartments 232 and 234. The diaphragm 230 is alsoconnected to spring 226. The compartment 232 communicates with theatmosphere through a vent opening 236 in housing 202 and houses spring226. The compartment 234 is in fluid communication with liquified gasfrom a tank through an inlet conduit 238. The chamber 208 is incommunication with a vaporizer/engine through an outlet conduit 240. Thechamber 208 is also in bidirectional communication with the vaporholding portion of the tank through a conduit 242, which communicateswith an opening 244 in housing 202.

During operation of a liquified gas delivery system such as shown inFIG. 2, which employs valve 200 in place of economizer valve 38, a tankis filled with a fluid that has a low saturation pressure such as aliquified gas. If the tank is at lower pressure conditions and pressureset screw 224 is set at a much higher pressure, the difference betweenthe tank and atmosphere deforms diaphragm 230 downward, thereby movingspool 210 such that passageway 216 is opened, with opening 244 beingsealed by head portion 212. This allows liquified gas to flow from inletconduit 238 and compartment 234 into chamber 208 and through outletconduit 240 to the vaporizer/engine, with the passage from the vaporholding portion of the tank to the vaporizer/engine being closed.

A false head pressure is generated when a pressure drop is createdacross check valve 222 in spool 210. This pressure drop opens checkvalve 222, which allows a small quantity of liquified gas to passthrough shunt channel 220 and into vapor conduit 242 toward the vaporholding portion of the tank. This small quantity of liquified gas isvaporized from the heat added as it passes back into the tank. The addedheat increases vapor pressure and thus tank pressure. Since there isessentially no natural pressure drop across check valve 222, one iscreated from the dynamics of vaporization of fuel going to the engine.This process continues until the tank pressure, spring force, andatmospheric pressures reach a force balance such that head portion 212of spool 210 is positioned to allow both liquified gas and liquified gasvapor to pass to the vaporizer/engine, which position is shown in FIG.13.

Should the tank be at higher pressure conditions than the set point as aresult of no usage, the force balance at the spring/diaphragm interfacewill render spool 210 in the full up position, thereby closingpassageway 216 and preventing liquified gas from entering chamber 208.This allows liquified gas vapor from vapor conduit 242 to pass throughopening 244 into chamber 208 and through outlet conduit 240 toward thevaporizer/engine. Thus, all of the fuel is directed to the engine fromthe vapor holding portion of the tank until a force balance is againachieved.

FIG. 14 is a cross-sectional view of a valve device in the form of anecoshunt valve 250 according to another alternative embodiment of theinvention which is electrically controlled. The valve 250 is anotherexample of a control means which performs the function of automaticallywithdrawing a select gas from the tank based on the pressure within thetank.

The valve 250 includes similar components as discussed above for valve200, including a housing 252 having an interior surface 254 bounding apair of first and second interior chambers 256 and 258, which areseparated by a dividing wall 259. A proportioning spool 260 is disposedbetween chambers 256 and 258. The spool 260 includes an enlarged headportion 262 disposed in chamber 258 which tapers to an elongated stemportion 264 that extends into chamber 256 through a passageway 266 individing wall 259. A shunt port 268 in stem portion 264 communicateswith a shunt channel 270 which passes through head portion 262. A shuntcheck valve 272 is provided in channel 270 to regulate the flow ofliquified gas through channel 270. The chamber 256 is in fluidcommunication with liquified gas from a tank through an inlet conduit238. The chamber 258 is in communication with a vaporizer/engine throughan outlet conduit 240. The chamber 258 is also in bidirectionalcommunication with the vapor holding portion of the tank through aconduit 242.

As shown in FIG. 14, valve 250 utilizes an electrical actuation deviceas a means for positioning spool 260 rather than a pressure set screw asin valve 200. Accordingly, an electrical control coil 274 is provided ina third chamber 276 defined by housing 252 and a dividing wall 278separating chamber 276 from chamber 256. The stem portion 264 of spool260 extends into chamber 276 and a positioning spring 280 is configuredaround stem portion 264 adjacent to control coil 274. A power input 282from a power source (not shown) is operatively connected to control coil274. This approach makes valve 250 more readily adjustable, with valve250 capable of being controlled by a computer or a simple pressureswitch. The valve 250 and chambers therein are also hermetically sealedby housing 252, which means there are no dynamic parts that can failsuch that fuel would be released into the atmosphere.

The valve 250 functions in a similar manner as described above for valve200 in that valve 250 proportions fluid flow between an all gas phasefluid and an all liquid phase fluid, while directing available excessliquid phase fluid into the pressure building process. During operation,the pressure is set by electrical actuation of control coil 274 whichadjusts the position of spool 260 through magnetic interaction with stemportion 264 and spring 280. If the tank is at low pressure and thepressure is set at a much higher pressure, the difference between thetank and the set pressure causes spool 210 to move such that passageway266 is opened. This allows liquified gas to flow from inlet conduit 238and chamber 256 into chamber 258 and through outlet conduit 240 to thevaporizer/engine.

A false head pressure is generated when a pressure drop is createdacross check valve 272 in spool 260. This pressure drop opens checkvalve 272, which allows a small quantity of liquified gas to passthrough shunt channel 270 and into vapor conduit 242 toward the vaporholding portion of the tank. This small quantity of liquified gas isvaporized from the heat added as it passes back into the tank, thusincreasing tank pressure. This process continues until the tankpressure, spring force, and set pressure reach a force balance asdescribed previously. Should the tank be at a higher pressure than theset point, the force balance will render spool 260 in the full upposition, thereby closing passageway 266 and preventing liquified gasfrom entering chamber 258. This allows liquified gas vapor from vaporconduit 242 to pass into chamber 258 and through outlet conduit 240toward the vaporizer/engine until a force balance is again achieved.

FIG. 15 is a cross-sectional view of a valve device in the form of anecoshunt valve 300 according to a further alternative embodiment of theinvention which is electrically controlled. Like the other ecoshuntvalves previously discussed, valve 300 is also configured to perform thefunction of automatically withdrawing a select gas from the tank basedon the pressure within the tank.

The valve 300 includes similar components as discussed above for valve250, including a housing 302 having an interior surface 304 bounding apair of first and second interior chambers 306 and 308, which areseparated by a dividing wall 309. A proportioning spool 260 is disposedbetween chambers 306 and 308. The spool 260 includes an enlarged headportion 262 disposed in chamber 308 and a stem portion 264 that extendsinto chamber 306 through a passageway 310 in dividing wall 309. A shuntport 268 in stem portion 264 communicates with a shunt channel 270, anda shunt check valve 272 is provided in channel 270. The chamber 306 isin fluid communication with liquified gas from a tank through an inletconduit 238. The chamber 308 is in communication with a vaporizer/enginethrough an outlet conduit 240. The chamber 308 is also in bidirectionalcommunication with the vapor holding portion of the tank through aconduit 242.

As shown in FIG. 15, valve 300 also utilizes an electrical actuationdevice as a means for positioning spool 260. The electrical actuationdevice is in the form of an electrical control coil 274 which isconfigured on the outside of housing 302 around a third interior chamber312 in which stem 264 of spool 260 moves. The chamber 312 is in fluidcommunication with chamber 306, and is bounded by a seal end cap 314constructed of a non-magnetic material. Suitable non-magnetic materialsfor end cap 314 include aluminum, titanium, nickel/titanium alloys, andsome stainless steels. The non-magnetic material of end cap 314 allowsthe magnetic field generated by coil 274 to control the position ofspool 260 through the magnetic coupling of coil 274 and stem 264. Apositioning spring 280 is configured around stem portion 264 adjacent tochamber 312, and a power input 282 is operatively connected to coil 274.

The valve 300 functions in a similar manner as described above for valve250 in that valve 300 proportions fluid flow between an all gas phasefluid and an all liquid phase fluid, while directing available excessliquid phase fluid into the pressure building process. During operation,the pressure is set by electrical actuation of coil 274 which adjuststhe position of spool 260. The configuration of valve 300 with coil 274on the outside of housing 302 allows for convenient maintenance andrepair of coil 274, which can be done without compromising the integrityof valve 300 which is sealed or the need to drain valve 300 prior tomaintenance or repair.

FIGS. 16A and 16B are schematic representations of alternativeembodiments for connecting a valve device, such as valves 200 and 250discussed previously, to a tank according to the present invention. InFIG. 16A, valve 200 is shown in a retrofit type connection to a tank 14,which is filled by passing liquified gas through an inlet 16. A vaporconduit 32 having bidirectional flow capability provides fluidcommunication between valve 200 and the vapor holding portion of tank14. Liquified gas flows through a supply conduit 44 to valve 200. Anexternal connection section 290 attached to tank 14 provides variousconduits and ports for each of inlet 16, vapor conduit 32, and supplyconduit 44 so that these components function properly. A transitionconduit 92 provides fluid communication between valve 200 and theengine. Each of these respective components shown in FIG. 16A functionin the manner as described previously.

In FIG. 16B, valve 200 is shown as an integrated part of a tank 14,which provides improved reliability and robustness to valve 200. Thevapor conduit 32 can be formed externally as shown in FIG. 16B, oralternatively, can be part of the internal structure of tank 14. Atransition conduit 92 provides fluid communication between valve 200 andthe engine as described above.

The present invention may be embodied in other specific forms withoutdeparting from its spirit or essential characteristics. The describedembodiments are to be considered in all respects only as illustrativeand not restrictive. The scope of the invention is, therefore, indicatedby the appended claims rather than by the foregoing description. Allchanges which come within the meaning and range of equivalency of theclaims are to be embraced within their scope.

1. A system for delivering liquified gas to an engine, the systemcomprising: a holding tank configured to receive liquified gas atsaturated conditions, the tank having a liquid holding portion and avapor holding portion; a valve device in fluid communication with theliquid holding portion and the vapor holding portion of the tank, thevalve device adapted to automatically withdraw a liquified gas or aliquified gas vapor from the tank based on the pressure within the tank;a vaporizer in fluid communication with the valve device; a deliveryconduit extending from the vaporizer to an engine; and means formaintaining an operating pressure within the vapor holding portion ofthe tank.
 2. The system of claim 1, wherein the valve device is aneconomizer valve.
 3. The system of claim 1, wherein the valve device isan ecoshunt valve.
 4. The system of claim 1, wherein the means formaintaining an operating pressure comprises a return conduit extendingfrom the delivery conduit to the tank.
 5. The system of claim 1, whereinthe means for maintaining an operating pressure comprises a secondaryvaporizer configured to receive liquified gas from the tank and returnliquified gas vapor to the tank.
 6. The system of claim 1, wherein themeans for maintaining an operating pressure comprises a shunt systemwithin the valve device.